In a known conventional single cylinder type hydraulic shock absorber that is interposed between a vehicle body and an axle of a vehicle in order to suppress vibration in the vehicle body, a piston that contacts an inner peripheral surface of a cylinder slidingly is attached fixedly to a tip end portion of a rod, and an oil chamber and a gas chamber are delineated by fitting a free piston slidingly within the cylinder (see JP08-159199).
A passage that connects two oil chambers delineated by the piston is provided in the piston, and an orifice or the like that applies resistance to a flow of working oil passing through the passage is interposed in the piston. When the piston slides within the cylinder, the working oil travels between the oil chambers through the passage. Thus, the hydraulic shock absorber generates a damping force.
In this type of hydraulic shock absorber, the gas chamber compensates for variation in the volume of the cylinder occurring when the rod infiltrates the cylinder or withdraws from the cylinder. A pressurized gas is sealed in the gas chamber, and the gas chamber maintains the working oil in the cylinder in a constantly pressurized state.